Control valve with operating position hold



Sept. 7, 1948. wt STEPHENS CONTROL VALVE WITH OPERATINGTOSI'I'ION HOLDFiled Oct. 21, 1946 ton reaches'its full stroke.

Patented Sept. 7, 1948 CONTROL VALVE WITH OPERATING POSITION HOLDWilliam '1. Stephens, Painecvllle, Ohio, auignor to Hydraulic ControlEngineering Cleveland, Ohio, a corporation of Ohio Company,

Application mm 21, 1940, 861111 No. 704,661

12 cum. (01. 277-57) This invention relates to manually operated controlvalves for hydraulic power cylinder systems, and more particularly tosuch control valvesfor automatically holding the valve plunger in eitherof the operating or; power positions until the full stroke of the pistonin the cylinder is achieved, after which the valve plunger returns toits neutral position where high pressure liquid is by-passed to a tankor reservoir to'release the load on the pump.

It is a general object of the present invention to provide a novel andimproved control valve for hydraulic cylinder systems.

More particularly it is an object of the invention to provide a controlvalve for hydraulic cylin the valve'housing and the provision of areason the valve plunger within said chambers for effecting the holdingoperations.

Other and further objects and features of the invention will be moreapparent to those skilled in the art upon consideration of theaccompanying drawings and following specification, wherein is discloseda single exemplary embodiment of the invention, with the understandingthat it may be applied in a similar manner to various other valveembodiments without departing from the spirit of the invention.

In said drawing the single figure is a longitudinal central sectionthrough the valve housing and valve plunger, the latter beingillustrated-in central or neutral position.

In the operation of simple hydraulic power cylinder systems the need hasoften been felt for 'a control valve which does not require the operatorto maintain it in the power positions manally after once having placedit there. This problem would not be difiicult of solution if it were notrequired that the valve be returned to the neutral position when thepower cylinder pis- To visualize'the improvement of the presentinvention it is necessaryto' first consider the hydraulic system usedfor actuating a small hydraulic power cylinder of the double actingvariety, such as are used in large numbers for manipulating earth movingand agricultural machinery from tractors and the like and for aninfinite variety of other industrial purposes. A constant volume pumpdriven by some prime mover takes liquid from a tank or reservoir anddelivers it to the manual control valve. when this valve has its plungerin the neutral or hold position, both ends of the cylinder are cut oil.from the pump and the reservoir. It is always desirable that the valvein this position provide an open by-pass so that the pump deliversliquid back to the tank, which relieves it from load when not needed andcirculates the oil through the tank to keep it cool. When the valveplunger is moved to either of its power positions for moving the pistonin the cylinder, the high pressure from the pump is connected to theappropriate end of the cylinder and the other end of -the cylinder isconnected through the valve to the reservoir. Valves for performing thisoperation are well known and for a full detailed description of one notsubstantially different from the one to which the present improvement isapplied reference should be had to my Patent No. 2,362,944, granted Nov.14, 1944, for Control valve for hydraulic systems.

The drawing in the present case shows a valve adapted for cooperationdirectly with the tank or reservoir by being mounted on the sidethereof. As a consequence fluid from the several low pressurecompartments, chambers or ports passes directly to the tank. Theconstruction can readily.v be modified to provide a piping or integralmanifold to lead to a port for connection to a pipe carryingthis liquidto a separate tank if desired. The details of these several features areunimportant and have not been illustrated.

Referring now to the drawing, there is shown at H! a suitable cast metalhousing having a continuous longitudinal bore I2 of uniform diameterextending from end to end and adapted to receive a cylindrical,reciprocable valve plunger II with a close working flt therein. The borel2 traverses a plurality of chambers within the housing arranged insymmetrical form in pairs about a single central chamber l5, which maybe considered a discharge chamber, leading by means of a port (notshown) directly to the tank or reservoir. A high pressure chamber l6supplied by fluid from thepump through port I! has tributaries l9 and 20straddling the discharge chamber li. Spaced outwardly from thesetributary chambers are the power chambers 2| and 22, each adapted to beconnected by suitable piping attached to power ports 23, 24 respectivelyto the opposite ends of the power cylinder. These power ports may bedistinguished as advance" and retract. Next beyond these power chambersare the low pressure chambers 26 and 26 substantially at the ends of theplunger and housing. Chamber 26 is closed by threaded cap 21, the innerannular edge of which forms one abutment for the centering spring 23fitted about the reduced diameter end portion 3| of the plunger. Awasher slidable on this reduced portion abuts the inner edge-of thehollow cap 21 while a similar washer at the opposite end of the springabuts either the shoulder 33 at the junction of the two diameters of theplunger or the right end wall of the chamber 25. A plug 35 closes a borein the left end of the plunger and has a flange forming an abutmenttoengage the left face of the outer washer. It will be seen that thisconstruction permits the valve plunger to be manually manipulated ineither direction from the central position shown, and in each case thespring is loaded so that the plunger is returned to the central positionwhen released.

The right hand end of the plunger is provided with a reduced diameterstem 28 which passes through the low pressure chamber 26, and throughthe bushing 36 pressed into the bore l2 outwardly thereof. It alsoextends through the packing unit 32 secured in the outer end of the bore|2. The external end of this stem portion receives an eye 34 screwedinto the hollow end thereof for the attachment of an operatin link orthe like for manipulating the valve.

Adjacent the reduced ends the plunger is provided with full diameterlands 36 and 31, which in the neutral position shown isolate the powerchambers 2| and 22. A central land 38 of small longitudinal extent isineffective in the neutral position, but when the valve is pressed tothe left or right engages respectively with the bore portions 39 or 40and cooperates with the appropriate land 36 or 31 to isolate thedischarge chamber from the tributaries to the high pressure chamber l6.In the position shown it will be seen that high pressure fluid flowsfrom the tributaries through the grooves 4| and 42, in the plunger, tobe discharged in the chamber l5 and thence to the tank, but thisoperation is prevented when the plunger is moved in either direction asjust described.

Assuming the plunger to be moved to the left, it

will be seen that high pressure fluid will flow into the chamber 43 inthe left end of the plunger through radial bores 44 in the bottom of thegroove 4| and will lift the check valve 46 against its spring 46. Thispermits high pressure fluid to be discharged through radial passages 41emergin from the surface of the land 31 and now registering with powerchamber 2|. This will deliver high pressure fluid to the desired end 7of the power cylinder while fluid returning from the other end thereofby operation of its piston will enter power chamber 22, which is now incommunication with low pressure chamber 26, via.

and 64. These passages are adjustable in size by means of the threadedmetering pins 66 and '4 respectively. The pins extend to the outside ofthe housing and are fitted with kerfs for adjustment with a screwdriver. They are covered by acorn nuts and proper sealing gaskets toprevent leakage.

With the valve plunger positioned to the left as just described thereturning fluid from the inactive side of the power cylinder inendeavoring to escape from low pressure chamber 26 via restrictedpassage 64 for return to the tank through discharge chamber 62 builds upa pressure in 26 which acts on the annular or differential area llbetween the two diameters of the plunger at the right end and holds theplunger in its displaced position until movement of the piston in thepower cylinder ceases. Such movement stops either because the pistonreaches the end of its stroke or some mechanical means prevents itsfurther movement at the pressure of the liquid delivered to it. Liquidthen drains from chamber 26 and the pressure therein drops to that ofthe tank, which is substantially atmospheric, and the centering spring29 takes over and returns the valve plunger to the neutral positionshown. The pressure in chamber 26 is never permitted to be-- come sogreat as to prevent the operator from manually returning the valveplunger to the neutral position if he desires to stop the operation ofthe power cylinder intermediate the length of its piston stroke.

For operation in the opposite direction the conditions are just reversedfrom those described and the pressure in the chamber 25 and the hollowin cap 21 acts on the whole area of the plunger for holding the same inthe hoist position. In order that the fluid may readily pass the washerabutting the shoulder 33 several by-pass ducts 60 are provided as shown.

The amount of restriction effected by the meterin pins may be varied tofavor any flow conditions up to the capacity of the valve and may also,by proper adjustment, equalize to holding" effort on the two ends of theplunger even though the holding pressure is effective on different areasof plunger.

Valves of the type just described are particularly helpful in theoperation of tractors and small vehicles equipped with hydraulicallyactuated accessories, for in such cases the operator is very often inneed of more hands and feet than the normal person possesses in order tosuccessfully manipulate both the vehicle and accessories. This isespecially true of a farm tractor reaching the end of a row, for whenthis occurs the operator must steer, declutch and shift gears on thevehicle and at the same time must operate one or more control valves topull to plow or other implement out of the ground to prevent it frombeing damaged by the lateral movement on the turn. In the case of theconventional form of hydraulic valve one hand must be kept on thecontrol lever until the implement is entirely free of the ground. Theoperation is not a. rapid one because of the economic necessity of asmall pump. Hence it becomes quite a problem to steer and shift gearswith the remainin hand. The automatic hold feature incorporated in thepresent valve eliminates the need for the operator having to hold thevalve actuating lever in position more than long enough to startmovement of the power cylinderpiston, for then the returning liquidimmediately takes over and substitutes for his hand until the fullstroke of the piston has been achieved. Then the operating valve returnsto neutral, permits the pump to be relieved to the tank and holds thelifted implement immobile until the reverse operation lowers it..

I claim:

1. In a control valve of the type'descri'bed, in combination, a housing,a chamber therein for high pressure liquid, a pair of power chambers, apair of low pressure chambers, a bore intersecting all of said chambers,a valve plunger operatively positioned in said bore and so constructedand arranged that in the neutral" orcentral position the power chambersare isolated, and in either "power or. end position one power chamher isconnected to the high pressure chamber and the other to one of the lowpressure chambers, a restricted vent for each low pressure chamberwhereby pressure may be built up therein when connected to a powerchamber, an area on each portion of said plunger extending into said lowpressure chambers adapted to be sub- Jected to the built-up pressuretherein to hold the plunger in the power position to which it has beenmanually moved and a centering means for said plunger of insufiiclentstrength to overcome of said centralizing means.

3. In a hydraulic control valve, in combination, a housing having a highpressure inlet chamber, a liquid return chamber and two power chambers,a valve plunger, resilient means to centralize said plunger in saidhousing, said plunger being selectively movable manually to either sideof center position to connect one hoist chamber to the inlet chamber andthe other to the liquid return chamber, means restricting the flow ofliquid between said last mentioned chambers to build up a holdingpressure, and a surface at each end of said plunger arranged to beselectively subjected to said pressure when the valve plunger is movedfrom its central position to maintain it against the centralizing means.

4. In a valve for use between a pump, a double acting power cylinder anda tank, in combination, a housing having pump or inlet chamber, a tankor outlet chamber and two power chambers, a plunger reciprocable in saidhousing from a neutral central" to -either of two power positions andbeing constructed and arranged for cooperation with the housing in theneutral position to directly connect the pump and tank chambers and toisolate the power chambers and in either power position to connect onepower chamber to the pump chamber and the other to the tank chamber,resilient means to centralize the plunger in the housing, means to meterthe flow from either power chamber to the then connected tank chamber tocreate a liquid pressure and means cooperating with the plunger to usesaid pressure to hold the plunger in the power position in which it hasbeen placed.

bination, a housing having two power chambers and two low pressurechambers, a plunger reciprocable in said housing, resilient centralizingmeans for said plunger, each end of the plunger having an effective areaexposed in one of said chambers whereby pressure therein exertslongitudinal effort on the plunger, means to connect one of said lowpressure chambers to one of said power chambers when the plunger ismanually moved in one direction from the centralized position and viceversa, and a metered outlet for each low pressure chamber.

6. A control valve for use with a double acting power cylinder, a pumpand a tank and including, in combination, a housing having pump and tankports and advance and retract ports for connection to opposite ends ofsaid power cylinder, a plunger manually reciprocable in said housingfrom a central" to advance and retract positions, resilient meansbiasing said plunger toward central position, a separate low pressurechamber in the housing cooperating with each end of the plunger, meanson said plunger and housing to connect said tank and pump ports when incentral position and to connect the pump and advance or retract portswhen in one of the latter positions, and to connect the other of theadvance or retract ports to the corresponding low pressure chamber andmeans effective during liquid flow from the power cylinder into saidconnected chamber to apply a longitudinal pressure on said valve plungerto hold it in its oil central position against said biasing means. Y

7. A control valve for use with a double acting power cylinder, a pumpand a tank and including, in combination, a housing having pump and tankports and advance and retract ports for connection to opposite ends ofsaid power cylinder, a plunger manually reciprocable in said housingfrom a central to advance and retract positions, resilient means biasingsaid plunger toward central position, a separate low pressure chamber inthe housing cooperating with each end of the plunger, means on saidplunger and housing to connect said tank and pump ports when in centralposition and to connect the pump and advance or retract ports when inone of the latter positions, and to connect the other of the advance orretract ports to the corresponding low pressure chamber, each of saidchambers having an outlet, and a metering device for each outlet tomaintain a pressure in the chamber as long as there is adequate flowinto the same returning from the cylinder, each of said plunger endshaving an effective area available to the pressure in its chamber tohold the valve in selected 011 center position,

8. In a valve for controlling the flow of pressure and return liquid fora double acting power cylinder, in combination, a housing having areciprocable plunger therein, resilient means centering said plunger insaid housing, a pair of low pressure chambers in said housing, eachchamber surrounding an eifective end area on the plunger which area iscapable of reacting to pressure in the chamber to hold the shiftedplunger against centralizing after it is initially moved from center,and means to build up the pressure of returning liquid in the desiredone of said chambers when the plunger is shifted.

9. In a valve of the type described, in combination, a housing having abore, a plunger having lands and grooves reciprocable in said borebetween "central and power positions,

resilient centralizing means ifor said plunger, a high pressure inletand an outlet in said housing connected together by plunger grooves whenin central position and separated by lands when in power positions,spaced power cylinder ports and adjacent chambers in said housing, eachend of said plunger having an effective transverse area facing from thecenter and arranged in one of said chambers, means including saidgrooves and lands to connect one power cylinder port to said highpressure inlet and the other to its adjacent chamber when the plunger ismoved to either power position, and a restricted outlet for eachchamber.

10. The valve as defined in claim 9 in which said outlet is restrictedby means of an adjustable metering device.

11. In a control valve of the type described, in combination, a housinghaving an inlet port, an outlet means and two cylinder ports, a chamberfor high pressure liquid in communication with said inlet port, a pairof cylinder chambers, each in communication with one of said cylinderports, a pair of low pressure chambers, a bore connecting all of saidchambers, a valve plunger operatively positionable in anyone of threepositions in said bore and so constructed and arranged that whenpositioned in its central or "neutral position the cylinder chambers arefully isolated, and when positioned in either of its non-central or"power positions one cylinder chamber is connected to the high pressurechamber and the other to one of the low pressure chambers, a restrictedvent for each low pressure chamber forming the only communicationbetween said chambers and said outlet means whereby pressure may bebuilt up within a low pressure chamber when said chamber is connected toa cylinder chamber, an eflective pressure area on each portion 01' saidvalve plunger extending into said low pressure chambers and adapted torespond to the built-up pressure within the chamber to hold the valveplunger in the power position to which it has been moved and a centeringmeans for said plunger of insufilcient strength to overcome said holdingpressure.

12. In a valve of the type described, in combination, a housing having ahigh pressure fluid inlet port, a valve plunger movable in the housing,resilient means to longitudinally centralize said plunger in thehousing, chambers in said housing spaced on opposite sides of the centerthereof, each end of the plunger having an effective lateral areaexposed in one of said chambers and facing away from the center wherebyfluid pressurein either chamber tends to move the plunger in thedirection of the other, a continuously open restricted discharge orificefor each chamber, means controlled :by movement of the plunger in eitherdirection from the central position to open an orifice to admit *fluidunder the influence of that entering the inlet port to the chamber inthe other direction from the central position to act on the exposedplunger area therein and hold the plunger against action of thecentralizing means.

T. STEPHENS.

